This invention relates to television apparatus, and more particularly to a system for providing a television display which portrays the path of motion of a moving object in an otherwise static scene.
In application Ser. No. 864,405 filed Dec. 27, 1977, entitled "Television System For Displaying and Recording Paths of Motion" and assigned to the assignee of the present application, there is described a system for providing a television display which portrays the motion of an object in a scene during a specific time interval such that in addition to its present position being shown, a plurality of earlier positions, commencing with the start of the time interval, are also depicted. The system includes a storage device capable of storing one television frame and adapted to accept substitute information concerning individual picture elements of the television signal stored therein in combination with means for comparing a television frame stored in the storage device with selected subsequently arriving frames. Upon detection of differences between corresponding picture elements of the stored and subsequently arriving frames, signifying motion, the picture elements that caused the detected difference are substituted for corresponding picture elements in the stored frame, and the fact of each such substitution is stored or otherwise indicated. The system is arranged to preclude another substitution of previously substituted picture elements in the stored frame. The frequency of the comparisons, that is, the number of incoming television frames between successive comparisons, is controllable and determines the spacing in the display between successive positions of the moving object.
Although the motion detector of the described system is sufficiently sensitive to detect small differences between the moving object and the static background to effect the substitution of picture elements in the stored frame, there are situations in which the substituted picture elements have such small contrast against the background that the ultimate display is less effective than desired. There is ample contrast in the case of a putted white golf ball moving relatively slowly across a green, for example, but in the case of a pitched baseball, which may have a velocity as high as 90 to 100 miles per hour, the motion is so fast that the television pickup camera cannot generate a full amplitude signal of the moving object. In other words, whereas the baseball held stationary in front of the television camera would appear full white in the display, when it moves at high speed the camera cannot generate the full white signal with the consequence that it appears grey, and thus is not as readily discernible in the display. Accordingly, if picture elements representing an object moving with a relatively high velocity with respect to a stationary background are substituted in the stored reference frame of the above-defined described system they will appear in the display at the low level of contrast initially detected by the camera, an undesirable result from the viewer's point of view.
The primary object of the present invention is to provide a system for improving the viewability of a television display of the kind described above, particularly in situations in which the object whose motion is to be portrayed is moving relatively fast over an otherwise substantially static background. Another more general object of the invention is to provide a system for emphasizing or enhancing selected portions of a television display relative to other portions.